This thesis sheds light on the causes and consequences of ethnic cleansing in the 20th century Balkans with particular reference to the former Yugoslavia in the 1990s. It suggests that although the causes of the expulsion of targeted ethnic minorities may be thought to be multifarious in so far as they may be traced inductively in past history, fear, security dilemmas, and ethnic nationalism - these correlations were not necessarily deterministic. This thesis argues that ethnic cleansing in the region was primarily a top down phenomenon and that it occurred when political leaders espoused it as a strategy of nation-state building. The politics of ethnic cleansing at the national level were intrinsically linked with the delineation of borders, control of territory and other resources, national security and the political organisation of the state with the view to granting rights and protections exclusively to the members of the dominant nation. Wars of ethnic cleansing were not autonomous but instead an instrument of policy - the state being central in their organisation and execution. Their central feature was coercion. Hence, military operations relied not on direct combat with opponents but on the demonstrative capacity of violence, which was intended to compel the targeted peoples to leave. Although the Western powers' reaction to the expulsion of ethno-national minorities in the course of the 20th century has been inconsistent, the use of military means by the Western Alliance to reverse ethnic cleansing in Kosovo suggests that the policy of ethnic cleansing may no longer be countenanced, at least, in the European state system. In questioning the feasibility of creating states based on ethnic affinity as well as the validity of 'population transfers' and the partition of territory as viable tools of conflict resolution, the thesis establishes an agenda for policy making and future research.